GreatWhiteHunter,
I definitely do not get the amount of snow in VA and NC that you folks get in CT. However, my trucks have been through enough rain, snow, sleet, mud, dirt, sand, and hayfields to validate any environmental test you can throw at 'em. The compressor survived them all. The location that I am referring to is actually quite protected from the elements (at least on Crew Cab Fords). It is right in the vicinity of the passenger rear door. I mount the tank close to the corner of the pickup bed. One thing that I do is mount front mudflaps. It reduces the amount of water, snow, and road debris that is kicked up. But, that far back on the frame, it is out of the way anyway. The heat generated by the compressor motor will keep it from freezing. Yes, if you purchase the complete kit, it will come with a pressure switch.
I'll have to see if I can locate a picture of the bottomside of the truck with the tank and air compressor.
If you do run a tank, you might want to consider using the 1/4" coiled hose coming out of the tank(output). The lines running from the compressor to the tank (input) are generally 1/4". If you use the typical 1/2" and 3/4" hose, the compressor will not be able to pump air quick enough into the tank to maintain the volume required to keep enough pressure going into the tire, or whatever you are pumping up.
As far as life expectancy, I did have issues with my first two compressors. But, I think was just using cheap compressors. I never had any issues with either of the compressors that I put on my '01 and '06. Both were the Ride-Rite Systems.
In the attached pictures, you can barely make out the tank underneath the truck between the front of the fender and the rear running light. The compressor is hanging on the frame behind that last running light.